Geochronology and geochemistry of the Miocene volcanics from the Kutahya area: Constraints for post-collisional magmatism in western Anatolia, Turkey

Abstract

The first geochronological and geochemical data are presented for the Kutahya area volcanics in western Turkey to study mantle sources and magmatic processes. Petrographically, the studied volcanics are composed primarily of olivine augite basalt and augite basalt, with minor basaltic andesites/trachyandesites, and show porphyric, hyalo-microlithic porphyric and rarely glomeroporphyric textures. The rock samples contain plagioclase as phenocrysts and microlites, olivine, augite and biotite as phenocrysts, sanidine, opaques, and volcanic glass. Whole-rock K-Ar dating of the studied volcanics yielded cooling ages between 20.1 +/- 0.7 and 17 +/- 0.5 Ma (Early Miocene). The volcanics indicate magma evolution from shoshonitic to medium-high-K character. High contents of LILEs and LREEs, and low amounts of Nb, Ta, Zr and Ti indicate that fractional crystallization and assimilation processes had a role in the evolution of these volcanics. The studied volcanics also have moderate to high Sr-87/Sr-86 (0.70719-0.70971), negative epsilon Nd values (-6.27 to-4.63), and high( 206)Pb/Pb-204 (18.93-19.05), Pb-207/Pb-204 (15.69-15.76) and Pb-208/Pb-204 (38.99-39.32) ratios. Integrated trace element geochemical and Sr-Nd-Pb-O isotopic data suggest that the Kutahya area volcanics evolved via AFC processes from parental magma (s) that originated from a subcontinental veined lithospheric mantle source metasomatized by subduction-related fluids and melts.